When a work machine is to be taken into use at the intended location, it is not seldom that the problem arises that the location in question lacks a fixed electricity distribution grid for low voltage that can supply the required power to the work machine, i.e. the grid provides the required grid voltage, such as 400 V, but cannot supply the grid current that the work machine requires. This condition is known as “power deficit” and can arise when the available electricity distribution grid at the location can supply, for example, only a main fuse rating of 16 A while the work machine requires a higher fuse rating, for example 32 A, in order for it to be possible to use the machine. Thus, starting to use the work machine is considerably delayed or made more difficult, or in the worst case made impossible, in those cases in which the electricity distribution grid at the location cannot supply the current that the work machine requires. It should be understood that it is extremely troublesome if the work machine cannot be taken into use at the location immediately, also in those cases in which it is possible to modify or adapt the electricity distribution grid such that it is able to supply the current required to the work machine. In the worst case, it is not possible for the work machine to be driven off of the transport vehicle with which it has been transported to the relevant work location, due to the lack of the required electricity distribution grid. It should further be realised that the requirement for greater grid current and thus higher fuse rating than the rating available at the relevant location of the electricity distribution grid not only involves increases in cost as such, but also places considerably greater demands on the external electrical grid, with demands on the required conductor area, protective conductors, etc., that is to provide current to the electricity distribution grid at the location. The requirement to be able to drive and move the work machine during a limited period may, of course, also arise in the event of a sudden power failure or more extended loss of grid power.
EP 2 180 576 A2 reveals a portable power supply system for a remotely controlled electrically driven work machine. The system uses a coupling arrangement with current breakers or switches. An operator can reconnect the switches through the influence of a control arrangement such that they either connect in a primary source of power (the fixed alternating current electricity distribution grid at the location) or a secondary source of power (that may comprise a battery).